#include <stdio.h>
#include <stdlib.h>

struct nlist {
	struct nlist *next;
	char *name;
	char *defn;
};

#define HASHSIZE 101

static struct nlist *hashtab[HASHSIZE];

/* hash */
unsigned hash(char *s)
{
	unsigned hashval;

	for (hashval = 0; *s != '\0'; s++)
		hashval = *s + 31 * hashval;
	return hashval % HASHSIZE;
}

/* lookup */
struct nlist *lookup(char *s)
{
	struct nlist *np;

	for (np = hashtab[hash(s)]; np != NULL; np = np->next)
		if (strcmp(s, np->name) == 0)
			return np;
	return NULL;
}

/* install */
struct nlist *install(char *name, char *defn)
{
	struct nlist *np;
	unsigned hashval;

	if ((np = lookup(name)) == NULL) {
		np = (struct nlist *)malloc(sizeof(*np));
		if (np == NULL || (np->name = (char *)strdup(name)) == NULL)
			return NULL;
		hashval = hash(name);
		np->next = hashtab[hashval];
		hashtab[hashval] = np;
	} else 
		free((void *) np->defn);
	if ((np->defn = (char *)strdup(defn)) == NULL)
		return NULL;
	return np;
}

main()
{
	struct nlist *np;

	install("apple", "RINGO");
	np = lookup("apple");
	printf("%s: %s\n", np->name, np->defn);

	exit(0);
}